The present invention relates to AC-type plasma display apparatuses, and more particularly to an AC-type plasma display apparatus suitable for a display device carrying out an address discharge drive at high speed.
In the AC-type plasma display apparatus, a TV device to replace a conventional CRT as a display device having a large screen, being a thin flat type, and in light weight, has already been commercially produced.
Up to the present time, a Video Graphic Array TV having the number of lines of 480 pieces and belonging to a class of 40 inches in duration and a HDTV (abbreviation of High definition Tele-Vision) performing interlace scanning has been realized.
The AC-type plasma display apparatus, though already commercially finished in production, having a considerable number of subjects in terms of its performance, and has not yet excelled CRT in view of a quality of a picture.
As to the performance of a plasma display apparatus, in addition to basic performance required generally as a display apparatus such as display brightness, a contrast, resolution, a gray scale number, and consumption power, a problem in a quality of a picture of a dynamic picture has, in recent years, been encountered.
In a display method of gray scale of a plasma display apparatus, since time duration modulation by a light emit time duration is utilized with respect to amplitude modulation of brightness such as a CRT, an intrinsic deterioration in a quality of a picture relative to a dynamic picture is generated. In order to improve the performance of these plasma display apparatus, it is necessary to drive a plasma display panel at high speed and to enlarge values of various parameters determining a quality of a picture.
In an AC-type plasma display panel of this sort, as everybody knows, three electrodes of display electrodes composed of a paired X electrode-Y electrode in parallel to each other and of an address electrode (A electrode) intersecting these display electrodes are formed, and a surface discharge type panel is constituted. Further, cells are being pixels are constituted at points of intersection of these display electrodes and the address electrodes arranged in rows in a shape of stripes, a considerable number of cells form a two dimensional matrix inside the panel. In a matrix panel such as a plasma display, common electrodes are formed in the cells in every respective lines.
In a display method of gray scale of the plasma display apparatus, a sub-field method is used. A gray scale is expressed by a light emitting time duration of total of one field by dividing time of one field into a plurality of sub-fields, by varying a light emitting time duration in respective sub-fields, and by combining the light emitting time duration of several sub-fields while controlling a light emission of respective sub-field.
For example, when one field is divided into eight sub-fields and ratios of light emitting time durations of respective sub-fields are constituted in such a manner as 1:2:4:8:16:32:64:128, the gray scale of 256 steps from starting 0 ending at 255 can be displayed by controlling whether these sub-fields are emitted light or not and combining the light emitting time duration of respective sub-fields.
The number of gray scales of a plasma display apparatus is determined by the number of the sub-fields. When fine scaling a display of brightness by increasing the number of sub-fields, a quality of a picture having smooth display can be displayed even for a picture image gradually changing the brightness.
In the plasma display apparatus at present, the number of gray scales of brightness is in a degree of 100 gray scales, it occurred such a phenomenon as that delicate changing of brightness smashed into black color when a dark picture image is displayed. In order to display a further fine gray scale even for a dark picture image, the number of 1024 gray scales is necessitated, even constituting it of 2 to the n-th power having the least number of the sub-fields, n is 10, that is, 10 sub-fields are necessitated.
Further, in a sub-field method like this, it is well known that a dynamic false contour noise which deteriorates the quality of picture in the dynamic picture, is generated. In order to reduce this, a method to make inconspicuous the dynamic false contour noise is employed by setting a code of weight of a sub-field as a code different from 2 to the number of power, by being held a redundant property to the code, and by changing a combination of the light emission in a sub-field of display lines or the cells.
For that purpose, the number of sub-fields much more numerous is required and the number of the sub-fields in a degree of 15 is ideal. Since one field of a TV signal is approximately 16.7 ms, it means that an increase in the number of sub-fields is a decrease in time assigned to one sub-field.
A driving method separated into three, such as a reset period, an address period, and a display sustain period is generally used for one sub-field. These periods are common periods in an entire lines of the display panel, this driving method is referred to as an ADS (address display separate method). One example of this driving waveform is shown in FIG. 4 and FIG. 5 and necessity of acceleration of a drive will be explained.
In FIG. 4, the entire X electrodes are commonly connected to one another, in the Y electrode, an IC circuit for the purpose of applying a scanning pulse to individual electrodes during an address period is connected to the Y electrode, sustain pulses in a display sustain period are simultaneously applied to entire Y electrodes.
During a reset period of a sub-field, a high voltage pulse (rectangular reset pulse) 100 equal to or more than 300 V is applied to the X electrodes as a reset voltage VR. Thereby, a strong discharge is generated during this period in the entire cells and electrons and ions, constituted as wall charges to respectively in the X electrodes and the Y electrodes, forming an electric field by wall charges themselves accumulated on the X electrode and the Y electrode.
When waveform of the rectangular reset pulse 100 are fallen down, a discharge (self erase discharge/reset discharge) is generated by this electric field, the wall charges are floated in a space and disappears through neutralization. According to this reset discharge, the wall charges of entire cells are reset. During a neutralizing period, voltages of the X electrode, the Y electrode, and the A electrode (address electrode) are set as altogether a GND level, and this neutralizing period is approximately 100 xcexcs.
Next, during an address period, scanning pulses 106 of a voltage Vy are sequentially applied to the Y electrodes, address pulses 108 of a voltage Va are applied to the A electrodes. In the cells at which the scanning pulses 106 and the address pulses 108 are overlapped with each other, discharges between the electrodes A-Y are generated, the discharges between the electrodes X-Y are generated by being triggered by the discharges between the electrodes A-Y, the wall charges are formed on the X electrodes and the Y electrodes.
During a next display sustain period, sustain pulses 102 and 104 of a voltage Vs are alternately applied to the X electrodes and Y electrode and only for the cells formed the wall charges during an address period, the discharges are selectively generated, and display light is emitted.
This much is a light emitting mechanism of one sub-field, during the address periods, as illustrated in FIG. 5, the scanning pulses 106 are sequentially applied from a Y1 electrode to a Y 480 electrode (VGA is estimated). Accordingly, the display apparatus in which the number of lines being numerous (for example, in HDTV, equal to or more than 1000 pieces) the scanning pulses 106 equal to the number of lines must be applied.
However, in the address discharge generated by the scanning pulses 106, there is a time delay or there is dispersion depending on the cell, a time duration of a certain degree is necessitated in order to obtain reliability of a display. For example, in a VGA display apparatus, the time duration of the scanning pulses 106 is 2.4 xcexcs, in a case of HDTV display apparatus, having the number of lines 1000 pieces, the address period reaches 2.4 ms. The address period is necessitated to the entire sub-fields, when there are 8 sub-fields, time of one field portion are filled with only the address periods.
As described above, the address periods are required to be shortened in order to obtain a display of multi-sub-field arrangement (increase in the number of sub-fields) or a display of high precise arrangement (high density arrangement by decrease in size of cell and an increase in the number).
In order to realize these, there is a method to conduct interlace scanning. That is, a display of one field is made in a display of on every other line, the number of lines to be addressed are reduced in a half, and high precise (HDTV) display is tried to be performed. However, in this display, a flickering phenomenon is generated, in particular, a line flicker is remarkable, and a quality of a picture is largely damaged.
Further, the other method of decreasing in the address periods, the address electrodes are separated to the upper section and lower section of the panel, a method to simultaneously drive two lines. However, in this method, since the number of the address electrodes are doubled, the number of an integrated circuit driver is doubled, there is a drawback that the cost of a product is increased.
As described in the conventional example, a decrease in an address period is required in order to realize a fine scale display of brightness even in a dark picture image by an increase in the gray scale number, to try a reduction in a dynamic false contour noise of a dynamic picture, to realize a high precise panel display apparatus. For that purpose, an address discharge is required to be accelerated.
Accordingly, an object of the present invention is to provide an AC-type plasma display apparatus further improving a quality of a picture of a display picture image by resolving conventional drawbacks, by realizing a high speed address discharge, and by realizing a multi-sub-field arrangement and high gray scale in order to solve the problems described above.
In order to achieve the object described above, in the present invention, in an address discharge drive of an AC-type plasma display apparatus, it is constituted as that equal to or more than one piece of pulses of a narrow width as a preset pulse is/are applied, prior to time applying a scanning pulse, with a voltage exceeding a discharge breakdown voltage determined by a wall charge of a reset discharge.
In terms of constitutional characteristics of an AC-type plasma display apparatus relating to the present invention, the gist of the present invention will be described further in detail by mentioning specifically in following items (1)-(5).
(1) In an AC-type plasma display apparatus characterized by including display electrodes composed of paired first electrodes and second electrodes in parallel with each other, address electrodes intersecting the display electrodes, and drive circuits conducting address discharges between the display electrodes and the address electrodes, wherein the drive circuit conducting the address discharge has a means for applying pulses equal to or more than one piece of a narrow width predetermined as preset pulses prior to time applying a scanning pulse applied to said display electrode, wherein an apply voltage of the preset pulses is set as a voltage value exceeding a discharge breakdown voltage value determined by a wall charge of a reset discharge.
(2) An AC-type plasma display apparatus as set forth in (1) described above is characterized by having a plurality of sub-fields within one field, by including a reset period at least make uniform a wall charge, an address period for writing-in, and a display sustain period for display light emission, in the sub-field described above, and by having a function for applying scanning pulses sequentially to an electrode corresponding to a display line during the address period,
wherein in the address period, the drive circuit conducting the address discharge has a means for applying pulses equal to or more than one piece of a narrow width predetermined as preset pulses prior to time applying the scanning pulse, wherein an apply voltage of the preset pulses is a voltage value larger than a discharge breakdown voltage determined by a wall charge formed after the reset period being terminated, and the preset pulses are sequentially scanned keeping a constant time interval with the scanning pulse.
(3) An AC-type plasma display apparatus as set forth in (1) described above is characterized by including a paired plurality of first display electrodes and second display electrodes in parallel with each other and a plurality of address electrodes intersecting said display electrodes, wherein at least the display electrode has a panel covered by dielectric layer, time of one field is divided into a plurality of sub-fields, and the sub-field has at least a reset period, an address period, and a display sustain period, wherein in case of conducting write-in by applying a scanning pulse to the first display electrodes during the address period and by applying an address pulse to the address electrode, the sub-field described above has a means for applying pulses equal to or more than one piece of a narrow width having the same polarity as the scanning pulse predetermined as preset pulses prior to time applying the scanning pulse applied to the first display electrode, wherein an apply voltage of the preset pulses is set as a voltage value exceeding an address discharge breakdown voltage.
(4) An AC-type plasma display apparatus as set forth in (1) described above is characterized by dividing one field into a plurality of sub-fields, by including at least a reset period, an address period, and a display sustain period, in the sub-field described above,
wherein during the reset period, in case of conducting write-in operation by applying an entire reset pulse accompanied by a self erasing discharge to the second display electrodes, by resetting a remained wall charge of a plasma display panel, and by applying a scanning pulse to the first display electrodes during the address period and by applying a scanning pulse to the first display electrode, the sub-field described above has a means for applying preset pulses equal to or more than one piece predetermined prior to applying the scanning pulse applied to the first display electrode, wherein an apply voltage of the preset pulses is set as a voltage value larger than that of the scanning pulse, and a voltage value exceeding a discharge breakdown voltage.
(5) An AC-type plasma display apparatus as set forth in (1) described above is characterized by dividing one field into a plurality of sub-fields and by including in the sub-field with at least a reset period, an address period, and a display sustain period,
wherein, during said reset period, the sub-field described above has a means for conducting a lamp wave reset discharge, resetting, and for lessening a terminated voltage value of the lamp wave is smaller than a voltage value of a scanning pulse applying during the address period and a means for applying pulses equal to or more than one pieces of a narrow width of a voltage value approximately similar to the scanning pulse predetermined as a preset pulse prior to time applied the scanning pulse, in case of application of a scanning pulse to the first display electrodes during the address period.
By applying the preset pulse described above, an address discharge of high speed can be realized by conducting an initial portion (growing process of Townsent) of growth of a discharge by this preset pulse, and by lessening a delay of an address discharge caused by the scanning pulse.
Further, a reset discharge is a rectangular discharge accompanied by a self-erase discharge, an address discharge of high speed can be realized by applying a voltage value of the preset reset pulse with the voltage value larger than a voltage value of the scanning pulse. This means that although the scanning pulse itself can not discharge without the address pulse, by enlarging a voltage of the preset pulse more than a voltage of the scanning pulse, and resulting in a voltage value of the preset pulse exceeding a discharge breakdown voltage even without the address pulse.
Further, an address discharge of high speed can be realized by setting a cycle of the preset pulse approximately similar to a cycle of the scanning pulse. Thereby, a signal processing circuit of an integrated circuit driver can be simplified, so that a reduction in circuit cost can be realized.
Further, an address discharge of high speed can be realized by making a duration of the preset pulse to such a degree of thin line duration as a discharge does not generated. Due to no generation of a discharge to the preset pulse, since formation of a wall charge will not occurs, a discharge is prevented from being inhibited at the next address discharge. Since this preset pulse carries out a growing process of Townsent only and carries out growth of a space charge only, an address discharge constitutes a discharge of small delay and with high speed.
Further, an address discharge of high speed can be realized by constituting a reset discharge being a lamp wave reset discharge, and by enlarging a voltage value of the preset pulse more than a terminated voltage of a lamp wave reset. With these constitutions, since a voltage value of the preset pulse exceeds a discharge breakdown voltage, a growing process of Townsent can be conducted by this preset pulse.
Further, an address discharge of high speed can be realized by lessening a terminated voltage of the lamp wave reset less than a voltage of the scanning pulse and substantially equalizing a voltage of the scanning pulse with that of the preset pulse. According to this, since the voltages of both of the scanning pulse and the preset pulse becoming the same potential, a constitution of a high voltage amplifying circuit to generate pulses can be simplified, therefore, a decrease in cost is possible to be realized.
Further, only growth of a space charge can be implemented, without discharging the preset pulse, by setting a pulse duration of the preset pulse being equal to or less than 0.5 xcexcs.
According to the present invention, there is an effect that an address discharge is capable of being driven at high speed by applying pulses equal to or more than one piece of a narrow width exceeding a discharge breakdown voltage prior to time of applying the scanning pulse, by carrying out growing process of Townsent with the preset pulses, and by increasing the number of space discharges.
Further, there is an effect that a signal processing part of a circuit driver can be simplified and a circuit of low cost is possible to be realized by attempting a cycle of the preset pulse to be substantially similar to a cycle of the scanning pulse.
Furthermore, there is an effect that a high voltage circuit can be simplified and is capable of being realized in low cost by lessening a terminated voltage of a lamp wave reset less than a voltage of the scanning pulse and by making substantially similar a voltages of the scanning pulse to that of the preset pulse.